Composite closures are widely used to seal food containers, for example wide mouth containers that are "retorted" after sealing. Such closures comprise a sealing disk or cover, usually of metal or alternatively plastic, which is encircled and housed within a separately formed molded plastic band or shell. The disk has a raised peripheral crown that presents a downwardly opening groove that contains a sealant or gasket for forming a seal with a sealing rim around the top or finish of the container. The shell holds the disk down on the container but is rotatable relative to the disk so as not to turn the disk on the container, which would greatly increase the torque required for opening or closing. This type of seal is relatively insensitive to the thermal expansion and contraction that occur during retorting. (In retorting, after the container has been filled it is heated to a temperature above about 220 degrees F. under external pressure to sterilize the food sealed in it.)
U.S. Pat. No. 4,813,561, which is incorporated herein in its entirety, shows a composite retortable closure having a metal disk with a raised peripheral bead. The bead presents a downwardly opening groove that contains a sealant or gasket material for making a seal with the top, outer, and/or inward surface of the rim of the container. The disk is rotatably housed within an encircling molded plastic shell having an inwardly projecting curved lip that extends to and engages the top of the bead of the disk. As the shell is tightened, the undersurface of the lip bears downwardly on the disk bead thereby forcing the sealant material into sealing engagement with the container rim. The '561 patent also describes a tamper indicating band around the lower edge of the shell. The band is connected to the shell by a line of weakness provided by a series of small frangible bridges, and includes an upwardly and inwardly projecting band retainer. Interengaging ratchet teeth are provided on the container and the inwardly facing surface of the retainer. When the closure is first opened, the interengaging ratchet teeth prevent the retainer from turning with the rest of the closure, which in turn causes the tamper evidencing band to break off along the line of weakness. The band then drops downwardly, thereby indicating at least partial opening.
U.S. Pat. No. 5,346,082, which is incorporated herein in its entirety, discloses a composite closure for a container. The closure has an outer shell with a half-toroidal lip that overhangs a bead around the periphery of an insert cover disk. As the closure is tightened on the container, the lip bears downwardly on the crown of the disk and urges the disk against the container rim. Reaction force uncoils the hook like a watch spring, and a visible gap develops between the inner edge of the lip and the disk. This gap provides a visible on-line indicator that the hook is exerting sealing force on the disk. The '082 patent also discloses an improved tamper evident band.
The '082 patent discloses channels for enabling water to drain or dry from the interthread space around the threads of the container and closure. The '082 patent disclosed a closure having a movable gap between the edge of the lip and the disk, and channels to promote draining and drying. The gap unwinds in response to tightening of the closure onto the container. It is a goal of the present invention to provide a composite retortable closure that has improved draining and drying characteristics.